A variety of types of streaming swimming-pools have been invented. In most conventional streaming swimming-pools, water current is generated with screw blades. For example, in Japanese Patent Laying Open Kokai No. H05-340117, a screw type of water current generator is arranged at one end of the swimming pool.
According to such a water current generator, water is pushed out by rotation of the screw blades. For that reason, the generated water current becomes to be a turbulent flow; and therefore, it is difficult to provide a uniform flow rate along the width direction, which is orthogonal to the flowing direction. That is, the water current is a spiral stream, so that a different type of water current is generated in the bottom-to-surface direction. It looks like the water is agitated in the swimming pool. It is difficult to regulate the water current well around the surface of the water.
Further, according to the conventional technology, a large amount of frictional drag is made between the screw blades and the water. As a result, it is required to use a large capacity of motor in order to provide enough energy of water current. In addition, to provide much energy of water current, the screw blades are rotated at a high speed. Such a high-speed rotation of screw blades results in cavitation, which makes noise and vibration.
In order to well regulate the water current in a swimming pool, another type of invention is described in Japanese Patent Laying Open Kokai No. H09-78865. According to the invention, partition walls are arranged at a water supply opening to regulate the water current. However, the water current is still generated using screw blades, therefore above mentioned problems can not be solved yet. If the partition walls are arranged to have a narrower distance between each two adjacent walls, the resistance against the water is increased.
According to the conventional technology, a streaming type of swimming pool includes a drain opening or receiving opening at the downstream end, facing a water supply opening at the upstream end. In the conventional swimming pool, the water travels from the upstream and to the downstream end, and a part of the water is reflected at an end wall of the downstream end. The reflected water current interferes with the forward water current, so that complicated water current may be generated in the swimming pool (swimming tank).